


The Changeling

by CrimDemon



Series: Undertale AU Ideas/Subplots [1]
Category: Fatalbirth, Undertale (Video Game)
Genre: Determination (Undertale), Doppelganger, Emotions, Gen, Protectiveness, Trapped, soul
Language: English
Status: Completed
Published: 2018-11-05
Updated: 2018-11-05
Packaged: 2019-08-19 11:40:20
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 3,538
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16533914
Author URL: https://archiveofourown.org/users/CrimDemon/pseuds/CrimDemon
Summary: A snippet of what happens within this universe. Good intentions pave the road to Hell, right? It's a shame this statement is true.





	The Changeling

**Author's Note:**

> Might I start by saying, this was actually based on a dream I had a couple of weeks ago. I am glad I wrote it down so I didn't forget it.
> 
> I decided to put it in an AU called Fatalbirth that I was working on. It's an AU where Frisk is a young woman who purposely went into the mountain to kill the monsters, due to her being manipulated by her family and raised to despise monsters even though she doesn't know them.
> 
> At least she was suppose to.

This wasn’t how this was suppose to go.  
  
Frisk was panting softly. Her ears were ringing. Red stains were covering much of her clothes, but she had to get up. She had to move. She had to keep herself from shattering. She was trying to catch her breath as her eyes drifted over to her two friends. The taller one was on the floor, calling out for the other and struggling to get up. The other one…  
  
Her gaze was soon directed at the shorter skeleton in front of her. The sight almost caused her to scream. If she had a voice to scream with.  
  
Sans was on his knee bones, still as a statue. Three long light blue bones were sticking out from the ground, going through different places in his skull. The fact that he wasn’t moving scared Frisk. It was like there wasn’t any indication of life at all.  
  
Frisk slowly pushed herself up as codes and glitches flew around her. She regretted asking Sans and Papyrus to join her, and regretted that she had gotten the two of them involved. She hated herself for that. But, it was not the time or place for self-loathing. Frisk felt dizzy as she got to her feet. She couldn’t even make out the words coming from above the the three of them. No. That wasn’t it. She was refusing to listen. She was determined to help her friends. The other could wait.  
  
She walked slowly to Sans, stumbling when she lost her balance. Everything hurt. Everything was sore, and she felt broken. But, she wouldn’t let that stop her. Even though her HP was steadily decreasing, she had to keep going.  
  
Frisk picked herself up again as a red pool started to form. She couldn’t die yet. Not until Sans and Papyrus were out of the data and back in Snowdin.  
  
She walked just a little further as she got to her pun-loving friend. He looked so deathly. He really did a number on himself, and she was partially to blame. The voice of Papyrus was getting louder as Frisk wrapped her hand around one of the bones. Her hand was trembling as she gently held Sans’ skull close to her, carefully pulling the bone out of his head.  
  
He was strong. She knew he was strong, so an attack on himself was surely nothing. Right? It was just that magic that paralyzed you, and nothing else. Right? Frisk thought that maybe if the bones keeping him in place were gone, he would be alright.  
  
Surely he would be fine.   
  
As Frisk completely pulled out the first bone, it faded into a blue light. Then, it was gone. She didn’t see any wounds after the bone was out. That gave her some hope. Her movements were excitedly frantic, but she tried to keep a gentle touch as she started to pull another bone out of Sans. Frisk had to handle him with care. One slip up, and it could mean dusting him on accident.   
  
When Frisk pulled out the second bone, the voice above them was louder and much easier to hear as the ringing finally stopped. “You think doing that will help him now?” the voice of the other shouted down at her.  
  
She chose to ignore them again. There wasn’t time to give the other person her attention.  
  
Grabbing onto the last bone, she could faintly see life returning to Sans’ skull. She sighed with relief as she softly pulled to get the last attack out of him. The end of the bone was nearly out when she felt something inside her scream. It was a chilling feeling, like they were being watched by a predator.  
  
Frisk was filled with dread.  
  
She shook her head to shake the feeling away, then pulled the rest of the bone out as the lights in Sans’ eye sockets slowly returned. He took a deep and sharp breath, his breathing heavy like he had forced air to stay inside. His leaned onto Frisk, his body limp as he glanced up at her with a dazed look. “kid, that you?” Sans quietly asked.  
  
He looked like he was wanting to get up, but his body refused to do so. Frisk quickly gave him a nod as he smiled at her. “i hope i didn’t hurt cha too badly,” she heard him say as she kept a hold of him. She rummaged around her coat pocket and pulled out two wrapped Nice Creams. Frisk held the treat to her mouth, before she ripped off the wrapper of one of them with her teeth.  
  
_‘You’re doing great!’_  
  
She quickly ate the first treat. It gave her an instance brain freeze, but at least it brought her HP up a little. Or at the very least it wasn’t going down anymore. She then tore the wrapper off of the other one and attempted it to give it to Sans. Frisk placed it against his lipless mouth as she receive a confused look through haziness.  
  
_‘It’s a beautiful day!’_  
  
“frisk, i don’t need that,” he said, before getting a dirty look from Frisk. It was a look that said, “Just eat the damn thing!” Sans managed to give her a lazy shrug. “but, if it’ll make you feel better, i’ll be ICE.”  
  
Just like strange magic, the Nice Cream was nothing. It always fascinated Frisk how Sans managed to eat stuff. He huffed through his teeth as he closed his eye sockets. “give me a sec to regain mobility,” he whispered, drowsiness evident in his voice. “i just need to…” Sans soon trailed off, a soft snore coming from him.  
  
Even at a time like this, he could sleep. That’s the lazybones for you.  
  
Frisk shifted around so she could lightly place Sans on the ground. She started to hear Papyrus’ cries again as he crawled his way to Sans. The figure laughed loudly. “Sans is going to die, you know,” the voice from above them shouted. “And you’re responsible!”  
  
As if on cue, Frisk felt a presence forcefully push itself into her mind. It felt like it was invading her consciousness and was digging a deep hole for itself. It was a disgusting presence that flashed images, and caused the scene from before to play out in her head like a movie. She tried to push back the images and the invading mass, but all that was doing was giving her a headache. It was a scene she didn’t want to relive again.  
  
[Frisk had been told by a mysterious man how to get into the codes. She was actually ecstatic about the knowledge, knowing it was a way to hopefully bring out the two people stuck in the data. In the Void.  
  
Her excitement made her sign language sloppy as she told Sans and Papyrus about what she heard. She told them how they might get into the codes and help some people there. Papyrus didn’t have a clue what Frisk was talking about, but Sans understood completely. He asked her how they would get into the Void.  
  
She silently thought it through, before gesturing for them to follow her.  
  
Sans nodded and then told Papyrus to go back to Snowdin. The tall skeleton was not having it, refusing to leave Frisk and his brother while they went into a place as scary sounding as the Void.  
  
Nope.  
  
The Great Papyrus wasn’t planning on going to Snowdin without the other two going with him. And with the thought of two people trapped somewhere with no way to get out…  
  
He would never let his lazy brother have that type of responsibility. At least not alone.  
  
Sans took a deep breath and held his skull in his hand for a long second. Then, he grinned at Papyrus and shrugged, telling him he could go. As long as he stayed close and stayed behind him.  
  
After further venture into the watery area, the three stumbled upon a door near the end of Waterfall. It was the door that the mysterious man had mentioned, Frisk was sure. The door wasn’t there before, so that had to be it. Frisk reached out to open it, but Sans stopped her. He gave her a big, but nervous smile. “hey, kid, let me go first,” he said as Frisk glanced over to him.  
  
It was weird. Sans wasn’t normally nervous. But, maybe the sight of the door did that to him. Eventually, Frisk nodded and backed away from the door a little, allowing the skeleton first passage.  
  
She signed a quick “be careful” gesture with her hands, in which Sans quietly laughed. “i know, i know.”  
  
Sans stared at the door for a minute as he held his hand to the doorknob. If what Frisk had heard is right, maybe he could get HIM out. It was a stretch, but if there was a small chance to pull him out of the Void, he was willing to try. He opened the door. Just like a vortex, the three of them were sucked in through the door as it closed shut behind them.  
  
The place, the Void, looked achromatic. Save for a few colors that glitched in and out of existence.   
  
Sans decided to look for the one he wanted to find first, but that was not who they found.  
  
The three instead found Chara, surrounded by glitches and codes. Her smile wasn’t like the one Frisk had seen in her dreams. No, that smile was not warm. It was not kind. And in the back of her head, she thought: that can’t be Chara.  
  
Then, the scene just turned into flashing images. Frisk tried to confront Chara, Sans trying to help. Chara manipulated Sans somehow and caused him to start attacking Frisk. Papyrus shielded Frisk and got the wind knocked out of him. Then with what control he had left, Sans used his magic on himself. A light blue attack he talked about, rending the person caught in it immobile without hurting them.]  
  
The images were pounding harshly within Frisk’s skull. Her head hurt, it hurt so much. She had to will herself to keep from passing out, but sleep sounded pleasant at that moment. She could just sleep the pain off. Pretend the whole thing was just one of her nightmares.  
  
No. She couldn’t sleep yet. Not yet.  
  
Frisk finally had in her to look up at the large tower of code, focusing her attention on the form on top of it. She could tell the figure’s gaze was not on her, but on Sans and Papyrus. She stepped in front of them and shielded them from it’s view. This action caused an animalistic growl from the figure above.  
  
“No matter what you plan to do, I’m taking them, missy,” the form barked as it jumped from the code tower and landed lightly on the ground. “No one else can have them, you hear me?!”  
  
Frisk glared at the person in front of her as she kept her body in place. She could hear Papyrus behind her shuffling and telling the unconscious Sans reassurances. His words tugged hard on her slowly whitening SOUL, causing her to stand in a more protective way. Standing on guard to watch what the figure would do.  
  
Chara, no, someone who took Chara’s form, was glancing fast between her and the skeletons. She wondered if their eyes would pop out. It was an unsettling sight, even more so with the grin it was giving her. “Step. Aside. Frisk.”  
  
The being calling Frisk by name and its growing smile startled her. She panicked and pulled out a butterfly knife from her skirt pocket, quickly opening it and holding it in front of her towards “Chara”. The form laughed at her, “Ha! You think that thing scares me?” It walked up to Frisk and before Frisk could stab it with the blade, it grabbed her by the neck. She was starting to cough and clench her teeth, but she tried slashing at the being anyway.  
  
No matter how many times she did so, it kept missing. Even when she thought she made a direct hit. It smirked at Frisk. “See?” it whispered. “Your weapon means nothing to me.” While the being held Frisk’s neck, it walked away from Sans and Papyrus. Frisk wanted so badly to call out the tall skeleton’s name, but only a wheeze and cough came out of her mouth. What could only be described as a gray bubble, large enough to house a single body, sprouted out of the ground.  
  
Frisk’s vision was getting hazy, but she could see the object out in the corner of her eye. “If you don’t let me have them willingly, then this is the only solution,” it said. She coughed a few more times and tried to breathe as she saw something strange. The Chara doppelganger’s form was changing. Her eyes widened at the sight.  
  
It… was taking her form. She tried once more to slash at the being, but blade did nothing to help. All she could do was watch as her vision blurred in and out. “Now then, this will do fine, yes~?” it purred as it finished with its transformation. It then threw her into the gray bubble and straightened itself up, brushing HER shirt and skirt.  
  
“Yes, this form will do fine, I think,” the doppelganger glanced towards Frisk and tilted it’s head. “A SOUL is harder to replicate, but I’ll just keep it how Chara’s looked.” It giggled with an unnerving cuteness as its head perked up. Sans grunted and sat up as the doppelganger and Frisk glanced over to the two skeletons.  
  
The fake fRiSk smiled wide and hurried to the two as it knelt down. It held out its hand for Sans to take as it signed “you okay now?” with its free hand. The skeleton groaned as he held his skull in his hands before answering, “i’m fine, kid.”  
  
Papyrus sighed softly with relief and smiled at his brother, giving him a big hug. “PLEASE DON’T SCARE ME LIKE THAT AGAIN, BROTHER!” he exclaimed with both relief and shakiness. Sans patted his brother’s back reassuringly and chuckled quietly. “sorry, bro, i didn’t mean to RATTLE you,” he said through a laugh. “SANS, I WILL LET THAT SLIDE SINCE YOU’RE ALRIGHT.”  
  
fRiSk smiled wide and mimicked laughter as well as it could. Papyrus released Sans from his embrace as he saw someone a little ways away, standing up and frowning. “HEY, SANS?” “yeah, bro?” “COULD WE STILL HELP THE OTHER HUMAN?”  
  
Sans glanced over to where Papyrus was staring. He could faintly see what looked like Chara in a bubble of some kind, and that she was pounding against it. It looked like she was trying to mouth something to the two of them.  
  
fRiSk signed the two of them “she’s beyond help, we should just leave her” as Sans stood up after his brother. Papyrus’ eye sockets widened at the words, opening his mouth to protest. Before he could say anything, fRiSk grabbed both of the brother’s hands and pulled them away from the young woman. She was practically skipping to get to the door that lead out into Waterfall. She didn’t even look back to give the woman in the bubble a second glance.  
  
But, skeletons did. They watched as Chara kept pounding on the inside of the bubble. Papyrus could even swear he saw the light of her eyes darken and tear up, before she collapsed to the ground. Her body was heaving up and down in a fast pace. Both of them, mostly Papyrus wanted to go back and console her. But, just like that, they all disappeared through the door frame as it slammed shut behind them.   
  
Frisk glanced up from between her hair, again wanting to yell out to them before they left. But, without a voice, her cries and pleas were silent. She clenched a fist on her chest. It felt like her SOUL was starting to crack and break. Why was it hurting like that?  
  
The bubble keeping her in place soon disappeared as the feeling of wanting to throw up surfaced. Or it more like she wanted to throw something somewhere. Frisk’s darkening eyes glanced down at the butterfly knife given to her as a gift. It was still held firmly in her hand, beckoning her. She sat up and started to reel her hand back to throw it.  
  
But, she stopped as she lowered her hand, sighing silently as she read the engraving on it. It usually helped her calm down. Albeit, not enough for THOSE feelings.  
  
‘Only use this when we’re not around to help, and try not to use it on anyone. - P&S’  
  
Another tug at her SOUL. When her friends left with the doppelganger, she felt an emotion so foreign to her. It was one she didn’t know, yet she despised like feeling already. And even though she didn’t know what it was, a word popped into her head and told her what it felt like: DESPAIR.  
  
~  
  
As the three stepped out of the door, fRiSk let go of Sans and Papyrus’ hands. She glanced around in awe as she giggled. She turned and stared at a worried Papyrus and a disgruntled Sans. She opened her mouth to speak, but remembered she wasn’t supposed to.  
  
She instead signed an excited “so where to now?” and waited for an answer. Sans narrowed his eye sockets at her, glancing towards Papyrus as he spoke. “SHOULDN’T WE TRY TO FIND THE OTHER PERSON, SINCE SANS WANTED TO?” The shorter skeleton chuckled softly, shrugging slightly. “we can wait on that, bro,” he said.  
  
Sans started to hear Papyrus say something else, but he turned back look at fRiSk. She seemed different to him. Something about her was throwing him off. What was it?  
  
“SANS!”  
  
Papyrus shouting his name distracted him for a moment, his attention immediately on his brother. “ye-yeah, papyrus?” Sans asked through a laugh. The tall skeleton frowned at him and crossed his arms, sighing softly. “I WAS TELLING YOU THAT I WILL GO HOME AND MAKE LINGUINI FOR US,” he spouted out. “WE SHOULD REGAIN STRENGTH TO LOOK FOR THAT SOMEBODY!”  
  
The taller brother nyeh-ed softly and started fast walking towards Snowdin. The young woman was about to join as Sans thought to look at her SOUL. Maybe being in there for that long did something to it.  
  
“hey, kid, stay here a sec,” he told fRiSk as she turned around with a confused look on her face. But, she walked right up to him, using her hands to ask him what was wrong. “i just want to check something, it’ll be fast.” She frowned at him but stayed still. Sans narrowed his eye sockets once more and looked her over.  
  
She looked the same, but… He didn’t remember her hair being that short. He tried to think of a logical explanation for that as he kept scanning her, thinking that maybe she cut it on accident when Chara attacked.  
  
When he looked down where her SOUL was, it concerned and confused him. Now, he knew something wasn’t right. The SOUL he saw, that he was looking at, was all red. It was a darker red, almost black. Frisk’s wasn’t like that at all. Hers was a gentler red with white plaguing some of it.  
  
Sans grew silent, a silence that almost caused fRiSk to blow her cover. Before she could sign a question, the silence shattered. “who are you?” His eye sockets were dark, devoid of the lights that were usually in them.  
  
The young woman laughed softly and nervously. She signed a quick bunch of words, “what do you mean? Frisk.”  
  
Sans glared at fRiSk, his smile now menacing. “don’t play dumb with me,” he grumbled. “you do know i can SEE what color you SOUL is, right?”  
  
fRiSk growled under her breath, cursing to herself. She should’ve just taken Frisk’s SOUL and used it. Her hastiness made her too eager to do that. She huffed and grinned at Sans and shrugged like he normally would. “Fine, you caught me.” Sans continued to glare as he asked once more, “last chance, who are you?”  
  
It was quiet for a moment, before it grinned unnaturally. “yOu KnOw ThAt DiSgUsTiNg FeELInG yOu GeT, tHe OnE tHaT mAkEs YoU wAnT tO hUrT fRiSk Or WhAt MaKeS hEr WaNt To HuRt AlL oF yOu,” it started, “ThE tHiNg YoU cAlL a DiSeAsE, tHaT’s Me.”  
  
“I aM nOt FrIsK oR ChArA,” the being with Frisk’s body said. “yOu CaN cAlL mE cOrRuM, a PlEaSuRe To FiNaLlY mEeT yOu In PeRsOn, SaNs.” In person? He wasn’t sure what that meant. He was about to ask, readying an attack when a thought struck him.  
  
If this thing wasn’t Frisk, then where did she…?  
  
A sudden realization hit him as a tight and painful knot formed in his stomach and in his SOUL. No, that can’t be right. That wasn’t her back there, was it? Sans glanced over his shoulder to look where the door was, his bones rattling a little as he saw the door was nowhere in sight.


End file.
